Various hybrid powertrain architectures are known for managing the input and output torques of various prime-movers in hybrid vehicles, most commonly internal combustion engines and electric machines. Series hybrid architectures are generally characterized by an internal combustion engine driving an electric generator which in turn provides electrical power to an electric drivetrain and to a battery pack. The internal combustion engine in a series hybrid is not directly mechanically coupled to the drivetrain. The electric generator may also operate in a motoring mode to provide a starting function to the internal combustion engine, and the electric drivetrain may recapture vehicle braking energy by also operating in a generator mode to recharge the battery pack. Parallel hybrid architectures are generally characterized by an internal combustion engine and an electric motor which both have a direct mechanical coupling to the drivetrain. The drivetrain conventionally includes a shifting transmission to provide the necessary gear ratios for wide range operation.
Electrically variable transmissions (EVT) are known which provide for continuously variable speed ratios by combining features from both series and parallel hybrid powertrain architectures. EVTs are operable with a direct mechanical path between an internal combustion engine and a final drive unit thus enabling high transmission efficiency and application of lower cost and less massive motor hardware. EVTs are also operable with engine operation mechanically independent from the final drive or in various mechanical/electrical split contributions thereby enabling high-torque continuously variable speed ratios, electrically dominated launches, regenerative braking, engine off idling, and multi-mode operation.
Conventional powertrains in general are responsive to operator torque requests as may be provided by way of conventional throttle linkages to an internal combustion engine. Modern powertrains rely on torque based controls to determine a torque request from an accelerator pedal position where the accelerator pedal is not mechanically operatively coupled to an engine (e.g. throttle by wire). Hybrid powertrains generally rely upon a mechanically operatively decoupled accelerator pedal in determining the propulsion torque request from the vehicle operator, which propulsion torque may be delivered in various contributory splits from the internal combustion engine and the electric machine(s). Similarly, hybrid powertrains may provide all or a portion of braking torque by controlling regenerative operation of the transmission electric machine(s) or by controlling the electric machines in a fashion to transfer vehicle energy to the engine and dissipate that energy via engine braking in response to operator braking requests. Hybrid powertrains, therefore, are generally responsive to both accelerator pedal and service brake pedal requests to provide output torque in accordance therewith.